An experimental view on PureB silicon photodiode device physics

Suligoj

ESSDERC 2019 - 49th European Solid-State Device Research Conference (ESSDERC)

et al. 2019

Pure boron deposited on silicon for the formation of p + n-like junctions was studied for deposition temperatures down to 50 °C. The commonly used chemical-vapor deposition method was compared to molecular beam epitaxy with respect to the electrical characteristics and the boron-layer compactness as evaluated by etch tests, ellipsometry and atomic force microscopy. Electrically, the important parameters are minority carrier electron injection into the p-type region and the sheet resistance along the boron-to-silicon interface which appear to be independent of deposition method for temperatures down to 300 °C. Only with molecular beam epitaxy did we succeed in producing substantial layers for the lower temperatures down to 50 °C. Also, at this very low temperature, p + n-like diodes were formed, but the suppression of electron injection was less efficient than at the higher temperatures. From simulations, assuming that the attractive electrical behavior is due to a monolayer of fixed negative charge at the interface, the concentration of holes needed to explain the I-V characteristics is estimated to be 1.4×10 11 cm -2 for 50 °C deposition and 1.1×10 13 cm -2 for 400 °C.

Section: B Low Temperature Pureb Depositionssupporting

confidence: 69%

Back-end-of-line CMOS-compatible diode fabrication with pure boron deposition down to 50 °C

Suligoj

ESSDERC 2019 - 49th European Solid-State Device Research Conference (ESSDERC)

et al. 2019

“…On the Si surface, boron resides as an adatom decreasing the number of dangling bonds [13], [14], while boron depositions were found to cause band bending at the interface typical of highly doped p + regions [13], [15], [16]. It is of great interest to find conditions which would preserve such a high concentration of holes at the interface, the structure of which has been shown to have a great influence on the electrical properties [17], [18].…”

Section: Limits On Thinning Of Boron Layers With/withoutmentioning

confidence: 99%

Limits on Thinning of Boron Layers With/Without Metal Contacting in PureB Si (Photo)Diodes

IEEE Electron Device Lett.

Hardeveld

et al. 2019

A little more than a monolayer-thick pureboron (PureB) layer was deposited on silicon at 250 • C by chemical vapor deposition (CVD), forming junctions with low saturation current. They displayed the same efficient suppression of electron injection as PureB diodes fabricated with a few nm-thick PureB layer deposited at 400 • C. Assuming high concentrations of acceptor states at the B-to-Si interface, induced by a fixed negative charge in the range from 5 × 10 13 cm −2 to 5 × 10 14 cm −2 , would be consistent with the experiments and device simulations that exhibit an efficient suppression of electron injection. Metallization of the B-layers was studied, showing that in many situations, thinning of the layer to monolayer thickness will lead to a significant increase in the electron injection.

“…This is equivalent to an extremely high surface doping concentration of around 10 22 cm −3 [21]. The emitter efficiency is a measure for how well the p-region suppresses the injection of minority carrier electrons from the substrate, and much of the experimental work has been dedicated to determining the resulting electron current [40]. The deposition conditions have a large influence with the temperature being the most important parameter.…”

Section: Boron Deposited On Simentioning

confidence: 99%

On the Many Applications of Nanometer-Thin Pure Boron Layers in IC and Microelectromechanical Systems Technology

Nanver

et al. 2021

j nanosci nanotechnol

An overview is given of the many applications that nm-thin pure boron (PureB) layers can have when deposited on semiconductors such as Si, Ge, and GaN. The application that has been researched in most detail is the fabrication of nm-shallow p+n-like Si diode junctions that are both electrically and chemically very robust. They are presently used commercially in photodiode detectors for extremeultraviolet (EUV) lithography and scanning-electron-microscopy (SEM) systems. By using chemicalvapor deposition (CVD) or molecular beam epitaxy (MBE) to deposit the B, PureB diodes have been fabricated at temperatures from an optimal 700 °C to as low as 50 °C, making them both front- and back-end-of-line CMOS compatible. On Ge, near-ideal p+n-like diodes were fabricated by covering a wetting layer of Ga with a PureB capping layer (PureGaB). For GaN high electron mobility transistors (HEMTs), an Al-on-PureB gate stack was developed that promises to be a robust alternative to the conventional Ni-Au gates. In MEMS processing, PureB is a resilient nm-thin masking layer for Si micromachining with tetramethyl ammonium hydroxide (TMAH) or potassium hydroxide (KOH), and low-stress PureB membranes have also been demonstrated.